床板が薄いようなので底上げしておきましたよ

#!/usr/bin/ruby1.9
# -*- coding: utf-8 -*-

ObjectSpace.each_object(Class).select{|i|i.method_defined? :floor }.each do|clazz|
    clazz.class_exec do
        alias_method :floor_old, :floor
        begin
            remove_method :floor
            def floor
                floor_old+0.2
            end
        rescue NameError
            remove_method :floor_old
        end

    end
end

p 1.floor
p Rational(10,1).floor
p 3.14.floor

1.2
10.2
3.2